The present invention relates to a submersible thrust bearing apparatus and, more particularly, to a thrust bearing portion in a submersible thrust bearing apparatus of a vertical type submersible motor for use in a submersible well pump.
The present invention relates to a submersible thrust bearing apparatus in which an improved thrust bearing is mounted to between a ring-like form thrust runner and a thrust frame of the submersible thrust bearing apparatus or an improved thrust bearing and an improved thrust frame of the submersible thrust bearing apparatus.
A conventional submersible thrust bearing apparatus is disclosed, in, for example, Japanese Patent Laid-Open No. 4920/1987, in which a tilting pad type thrust bearing apparatus is used.
This conventional tilting pad type submersible thrust bearing apparatus 107 includes, as shown in FIG. 12, a shaft collar 111 fixed to a rotative shaft 101 with a hexagonal nut 110, and a ring-like form thrust runner 112 inserted in the shaft collar 111. A bearing frame 115 is positioned in opposition to the thrust runner 112 and is supported with a pivot receiving member 113, with the bearing frame 115 being engaged with a rotative stopping member 114 so as to not rotate, and a thrust bearing 116 mounted to the bearing frame 115.
The thrust bearing 116 includes a plurality of sector form pads 117, positioned on the bearing frame 115 at a circumferential direction, with each of the pads 117 including a pin 18 at a central bottom portion thereof as shown in FIG. 13. The pin 118 extends into a hole 119 formed in the bearing frame 115 and can tilt and rotate with the bearing frame 115.
When the rotative shaft 101 rotates, the thrust runner 112 rotates also and, water flow is caused by the rotation of the rotative shaft 101, with the pad 117 of the thrust bearing 116 tilting at the circumferential direction against the thrust runner 112 due to the water flow. By virtue of the tilting of the pad 117, the tip of the pad 117 becomes higher at the rotation direction side against the thrust runner 112.
As a result, a clearance is formed at a space between the sliding face being formed on the lower surface of the thrust runner 112 and the sliding face formed on the upper surface of each pad 117. The clearance has a tapering wedge-shaped form at the rotation direction against the thrust runner 112. The wedge-shaped form clearance results in a dynamic pressure by the wedge effect and further forms water film therein, with all of thrust load (axial direction load) being then supported by the water film.
Accordingly, when the thrust load becomes large, the tilting degree of the pad 117 becomes small then the sliding face formed on the thrust runner 112 closely adheres to the sliding face formed on the pad 117.
As a result, the wedge-shaped form clearance becomes narrower, the occurrence of dynamic pressure by the wedge effect becomes smaller, and accordingly, hardly any water film is formed between the space of the sliding face formed on the thrust runner 112 and the sliding face formed on the pad 117.
This causes a large temperature increase in the space of the sliding faces, and the sliding face of the pad 117 is convexly deformed by the temperature differential caused between the temperature of the upper face of the pad 117 and the temperature of the bottom surface of the pad 117. Further, the sliding surface of the pad 117 is also convexly deformed by the thrust load itself.
The convex load deformation at the sliding face of the pad 17 further narrows the wedge-shaped form clearance, making even more difficult to form the water film. As a result, it becomes to be impossible to support the thrust load by the thrust bearing apparatus 107.
Therefore, to support the high thrust load it is necessary to provide a large submersible thrust bearing apparatus, however such approach requires high cost.